Crystalline aluminophosphates having uniform pore dimensions ranging from about 3A to about 10A are disclosed in U.S. Pat. No. 4,310,440. The chemistry of aluminophosphates, in general, is discussed in this patent at column 1, line 42 to column 2, line 58, inclusive. The novel class of aluminophosphates disclosed in U.S. Pat. No. 4,310,440 have an essential crystalline framework structure whose chemical composition expressed in terms of molar ratios of oxides is EQU Al.sub.2 O.sub.3 :1.+-.0.2P.sub.2 O.sub.5
said framework structure being microporous in which the pores are uniform and in each species have nominal diameters, the dimensions of which vary, among the individual species, from about 3 to 10 Angstroms (A). These crystalline aluminophosphates are described as having an intracrystalline adsorption capacity for water at 4.6 torr and 24.degree. C. of at least 3.5 weight percent and the adsorption of water is completely reversible while the essential framework topology is retained in both the hydrated and dehydrated state. The term "essential framework topology" means the spatial arrangement of the primary Al--O and P--O bond linkages. A lack of disruption of these primary bond linkages indicates that the framework topology has not changed.